17 June, 2013
Once in 5 years, the American Cancer Society publishes its updated guidelines on nutrition and physical activity in the context of cancer prevention . Among the detailed advice is the following quote: 'Limit consumption of sugar-sweetened beverages such as soft drinks, sports drinks, and fruit-flavored drinks.' How this general phrasing relates to specific cancer types is discussed below, and a recent study serves as a good starting point . The investigators evaluated the impact of dietary intake of sugary foods and beverages, as well as added sugar and total sugar on endometrial cancer risk in a population-based, case-control study, including 424 cases and 398 controls. Participants completed an interview and food frequency questionnaire and provided self-recorded waist and hip measurements. Women in the highest quartile of added sugar intake had significantly increased endometrial cancer risk (OR 1.84, 95% CI 1.16–2.92). Among women with waist-to-hip ratio ≥ 0.85, risk was significantly higher for the highest versus lowest tertile of added sugar intakes (OR 2.50, 95% CI 1.38–4.52). The association with added sugar also became stronger when analyses were restricted to never users of hormone replacement therapy (OR 2.03, 95% CI 1.27–3.26, for highest versus lowest tertile). There was little evidence of effect modification by body mass index or physical activity.
It is claimed that one-third of the cancer deaths that occur in the United States each year can be attributed to physical activity and diet habits, including the ill effects of overweight and obesity. The same risk factors are relevant for cardiovascular disease as well, which therefore creates a platform for the current global campaign to limit the use of sugary foods and drinks. It seems logical that high caloric intake may lead to overweight and obesity, which in turn are associated with increased cancer risk, but is there a direct link between sugary foods or beverages and cancer? The above study on endometrial cancer did find a significant association with high sugar intake but, in fact, there is a relatively paucity of data on this issue, and the existing data on cancer in general are not uniform . Being a growth factor, there is no surprise that hyperinsulinemia, in the set-up of insulin resistance, may be associated with the development of cancer . Chronic hyperinsulinemia in insulin-resistant patients increases bioavailability of IGF-I. Many clinical and epidemiological studies have shown that excess body weight gain, associated with hyperinsulinemia, insulin resistance and dyslipidemia, may be a major risk factor for certain types of tumors, including colon and breast cancer. However, a direct contribution of a high caloric intake or a high consumption of sugary foods and beverages to increased cancer risk should not automatically be assumed. As an example, it is well established that obesity is associated with increased risk for ovarian cancer , but data on the potential effects of diet in this respect are inconsistent. A recently published study supports the previous findings, as no evidence of an association between consumption of sugary foods and beverages and ovarian cancer risk could be established, although there was a suggestion of increased risk associated with sugary drink intake (each additional serving of sugary drinks per 1000 kcal: OR 1.63, 95% CI 0.94–2.83) . The investigators also pointed out that they did not find consistent evidence that sugar consumption and ovarian cancer risk were negatively impacted by central adiposity or excess weight.
The same cluster of the aforementioned risk parameters applies to breast cancer as well. In the Canadian National Breast Screening Study, a statistically significant positive trend was observed between energy intake and breast cancer risk (p (trend) = 0.01), but body mass index was not independently associated with breast cancer . There was evidence of an increased risk of breast cancer associated with a relatively high body mass index among postmenopausal women in the highest quartile level of energy intake (hazard ratio 1.72, 95% CI 1.01–2.93, p (trend) = 0.05).
Cancer prevention guidelines recommend a diet rich in fruits, vegetables and whole grains, recommend limiting sugary foods and beverages, red and processed meats, sodium and alcohol, and recommend avoiding foods contaminated with carcinogens. It is a pity, however, that young people, the best target population for implementing this dietary advice, typically do not meet the daily recommendations for fruit, vegetable, or whole grain consumption and are over-consuming energy-dense, sugary and salty foods . Once again, it is our duty as physicians to provide education on this important issue to our patients.
Department of Medicine 'T', Ichilov Hospital, Tel-Aviv, Israel
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